Moving paper carriage typewriters have been well known and well developed throughout the past. The escapement systems therein have typically used a moving and fixed dog arrangement to engage protruding stops on a ratchet wheel. The ratchet wheel has been fixed to a pinion for engagement with the paper carriage rack. With the advent of interchangeable type elements, such as are found on single element moving print carriage typewriters, the availability of dual pitch typewriters has become considerably more prevalent. It has been a desirable goal to implement a feasible and reliable dual pitch escapement system on moving carriage typewriters.
Techniques for implementing dual pitch escapement on moving print carriage typewriters differ substantially from that applicable to moving paper carriage typewriters and, as such, are not clearly adaptable for that purpose. Additionally, the requirement for a backspacing technique for moving paper carriage typewriters further creates difficulty in attempting to implement the moving carriage dual pitch system.
It is an object of this invention to backspace the paper carriage typewriter in such a manner that it may function properly and reliably regardless of which of two pitches the escapement system is operating in.
It is an additional object of this invention to select from the keyboard the increment of escapement through which the carriage of a moving carriage typewriter will displace upon the depression of any escaping key stroke.
It is a further object of this invention to reliably backspace the carriage regardless of the pitch from a single non-selectable keyboard initiated mechanical drive.